首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5349篇
  免费   330篇
  国内免费   16篇
耳鼻咽喉   98篇
儿科学   190篇
妇产科学   144篇
基础医学   811篇
口腔科学   117篇
临床医学   523篇
内科学   970篇
皮肤病学   61篇
神经病学   399篇
特种医学   330篇
外科学   970篇
综合类   27篇
预防医学   289篇
眼科学   179篇
药学   310篇
中国医学   10篇
肿瘤学   267篇
  2023年   32篇
  2022年   53篇
  2021年   124篇
  2020年   71篇
  2019年   110篇
  2018年   136篇
  2017年   92篇
  2016年   114篇
  2015年   132篇
  2014年   184篇
  2013年   213篇
  2012年   307篇
  2011年   319篇
  2010年   198篇
  2009年   175篇
  2008年   249篇
  2007年   242篇
  2006年   242篇
  2005年   266篇
  2004年   219篇
  2003年   216篇
  2002年   209篇
  2001年   143篇
  2000年   122篇
  1999年   114篇
  1998年   61篇
  1997年   46篇
  1996年   29篇
  1995年   33篇
  1994年   28篇
  1993年   29篇
  1992年   80篇
  1991年   65篇
  1990年   84篇
  1989年   64篇
  1988年   56篇
  1987年   53篇
  1986年   45篇
  1985年   71篇
  1984年   38篇
  1983年   40篇
  1982年   48篇
  1979年   43篇
  1977年   26篇
  1975年   32篇
  1974年   32篇
  1973年   35篇
  1972年   33篇
  1971年   25篇
  1968年   25篇
排序方式: 共有5695条查询结果,搜索用时 31 毫秒
71.
After experimental inoculation, severe acute respiratory syndrome coronavirus 2 infection was confirmed in bank voles by seroconversion within 8 days and detection of viral RNA in nasal tissue for up to 21 days. However, transmission to contact animals was not detected. Thus, bank voles are unlikely to establish effective transmission cycles in nature.  相似文献   
72.

There is agreement among health economists that on the whole medical innovation causes health care expenditures (HCE) to rise. This paper analyzes for which diagnoses HCE per patient have grown significantly faster than average HCE. We distinguish decedents (patients in their last 4 years of life) from survivors and use a unique dataset comprising detailed HCE of all members of a regional health insurance fund in Upper Austria for the period 2005–2018. Our results indicate that among decedents in particular, the expenditures for treatment of neoplasms have exceeded the general trend in HCE. This confirms that medical innovation for this group of diseases has been particularly strong over the last 15 years. For survivors, we find a noticeable growth in cases and cost per case for pregnancies and childbirth, and also for treatment of mental and behavioral disorders. We discuss whether these findings contradict the widespread interpretation of cost-increasing innovations as “medical progress” and offer some policy recommendations.

  相似文献   
73.
Köckerling  F.  Hantel  E.  Adolf  D.  Kuthe  A.  Lorenz  R.  Niebuhr  H.  Stechemesser  B.  Marusch  F. 《Hernia》2021,25(5):1169-1181
Hernia - There are hardly any studies on the outcome of scrotal compared with medial and lateral inguinal hernias. Therefore, this present multivariable analysis of data from the Herniamed Registry...  相似文献   
74.
75.
76.
77.
The key-enzyme for the metabolism of diamines in man is diamine oxidase (DAO). Its highest activities are in the intestinal mucosa, localized in the cytoplasm of the mature enterocytes of the small and large bowel. If the gut is affected by inflammation in Crohn's disease macroscopical changes are observed. This prospective study investigated if these mucosal alterations are also reflected in changes of mucosal diamine oxidase activity and/or mucosal histamine content respectively. Twenty patients (12 female, 8 male; age: , range 18 49 years) undergoing gut resection because of complications in Crohn's disease (Jan.–Dec. 1988) formed the basis of the study. Tissue samples of the resected material from areas inflamed and histologically not involved in the disease were investigated for diamine oxidase activities and histamine content. Diamine oxidase activities in the mucosa obtained from the macroscopically normal proximal (155.6; (76–393) mU/g ( range)) and distal (132; (58.5–295) mU/g) resection margins were similar to our previous findings. In all patients, however, samples from the diseased mucosa had significantly (ca. 50%) lower diamine oxidase activities (74.5; (5–262) mU/g) compared to the healthy tissue. Similar differences were found in material obtained either from whole intestinal wall or from the mucosa. The determination of diamine oxidase activity constitutes possibly a more unambiguous and earlier parameter for assessing the extent of the inflamed area than histological disease presentations. Using biopsies the necessary extent of resection could be estimatedbefore operation: this may influence operative strategies and help in the definition of the minimum amount of inflamed gut to be removed.Supported by grant of Deutsche Forschungsgemeinschaft (Lo 199/15-2).  相似文献   
78.
High exposures to organic solvents among graffiti removers   总被引:3,自引:0,他引:3  
Summary The exposure to organic solvents among 12 graffiti removers was studied. Health effects were also assessed by structured interview and a symptom questionnaire. Blood and urine samples were collected at the end of the day of air sampling. The concentrations of dichloromethane, glycol ethers, trimethylbenzenes and N-methyl-2-pyrrolidinone in the breathing zone of each worker were measured during one working day. The 8-h time-weighted average exposure to dichloromethane ranged from 18 to 1200 mg/m3. The Swedish Permissible Exposure Limit value for dichloromethane is 120 mg/m3. The air concentrations of glycol ethers, trimethylbenzens and N-methyl-2-pyrrolidinone were low or not detectable. No exposure-related deviations in the serum concentrations of creatinine, aspartate transaminase, alanine transaminase, -glutamyl transpeptidase or hyaluronan or the urine concentrations of 1-microglobulin, R2-microglobulin or N-acetyl--glucos-aminidase were found. Irritative symptoms of the eyes and upper respiratory tract were more prevalent than in the general population. This study demonstrates that old knowledge about work harzards is not automatically transferred to new professions. Another aspect is that the public is also exposed as the job is performed during daytime in underground stations. At least for short periods, bystanders may be exposed to high concentrations of organic solvent vapours. People with predisposing conditions, e.g. asthmatics, may risk adverse reactions.  相似文献   
79.
Based on biochemical and ligand binding studies in various tissues and species, evidence for several alpha 2-adrenergic receptor subtypes has accumulated. The current alpha 2-adrenergic receptor classification (alpha 2A, alpha 2B, alpha 2C) is based exclusively on pharmacological criteria. The molecular cloning of three distinct genes for human alpha 2-adrenergic receptors has confirmed the existence of multiple alpha 2-adrenergic receptor subtypes. According to their localization on different human chromosomes, the receptor genes were termed alpha 2-C10, alpha 2-C4, and alpha 2-C2. The relationship, however, between the pharmacologically characterized alpha 2-adrenergic receptors and the isolated genes has yet to be clarified. Using Northern blot hybridization, we analyzed the expression of the three cloned alpha 2-adrenergic receptor genes in 13 rat tissues, as well as in cell lines previously described as model systems for the pharmacologically defined alpha 2-adrenergic receptor subtypes. The alpha 2-C10 receptor corresponds to the alpha 2A subtype and is expressed in rat brainstem, cerebral cortex, hippocampus, pituitary gland, cerebellum, kidney, aorta, skeletal muscle, spleen, and lung. Messenger RNA coding for the alpha 2-C4 receptor was detected only in brain regions, not in peripheral tissues, whereas the alpha 2-C2 message was found only in liver and kidney. Hybridization experiments with RNA derived from tissues and cells from which the pharmacological alpha 2-receptor classification has been developed lead to the conclusion that the alpha 2B subtype represents two distinct receptor molecules, the alpha 2-C4 and a subtype previously undetected by classical ligand binding approaches. Furthermore, our results suggest that the alpha 2C subtype characterized in opossum kidney cells is an interspecies variation of alpha 2-C4 rather than a separate subtype. Finally, the cloned alpha 2-C2 receptor was found to be "alpha 2B-like" and not covered by the current pharmacological classification.  相似文献   
80.
T cell ignorance is a specific form of immunological tolerance. It describes the maintenance of naivety in antigen-specific T cells in vivo despite the presence of their target antigen. It is thought to mainly play a role during the steady state, when self-antigens are presented in absence of costimulatory signals and at low density or to T cells of low affinity. In how far antigen-specific T cells can also remain clonally ignorant to foreign antigens, presented in the inflammatory context of systemic infection, remains unclear. Using single-cell in vivo fate mapping and high throughput flow cytometric enrichment, we find that high-affinity antigen-specific CD8+ T cells are efficiently recruited upon systemic infection. In contrast, most low-affinity antigen-specific T cells ignore the priming antigen and persist in the naïve state while remaining fully responsive to subsequent immunization with a high-affinity ligand. These data establish the widespread clonal ignorance of low-affinity T cells as a major factor shaping the composition of antigen-specific CD8+ T cell responses to systemic infection.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号